View full sizeThen-Republican presidential candidate and former Massachusetts Gov. Mitt Romney takes the stage to concede his quest for president at the Boston Convention Center in Boston in 2012. (AP Photo/Stephan Savoia)

Former GOP presidential nominee Mitt Romney slammed possible future Democratic nominee Hillary Clinton Sunday, saying she repeatedly underestimated threats faced by the United States and that her answer to a question on the release of U.S. Army Sgt. Bowe Bergdahl was "clueless."

"This administration, from Secretary Clinton to President Obama, has repeatedly underestimated the threats that are faced by America," Romney told David Gregory. "It has repeatedly underestimated our adversaries. And whether that's Russia or [Syrian President Bashar] Assad or ISIS or al-Qaida itself, it has not taken the action necessary to prevent things from happening. We have not used our influence to do what's necessary to protect our interests."

Romney went on to say that Clinton's comments about Bergdahl showed that she doesn't have a grasp of what is a threat to the United States, and if the GOP wants to win the presidency in 2016, they merely have to run on her record if she is the Democratic nominee.

"She was asked whether the Bowe Bergdahl trade was one that presented a threat to the United States," Romney said. "And she came back with a clueless answer. She was clueless. She said, 'Look, these commandos don't represent a threat to the United States.' Well, of course they do. And then she went on to say, 'They only represent a threat to Afghanistan and Pakistan.' Are you kidding? I mean, we're in Afghanistan. And we're in Afghanistan in part to protect America's security."